
#include "json_pref_store.h"

#include <algorithm>

#include "base/bind.h"
#include "base/callback.h"
#include "base/file_util.h"
#include "base/memory/ref_counted.h"
#include "base/message_loop_proxy.h"
#include "base/value.h"

#include "json_value_serializer.h"

namespace
{

    // Some extensions we'll tack on to copies of the Preferences files.
    const FilePath::CharType* kBadExtension = FILE_PATH_LITERAL("bad");

    // Differentiates file loading between origin thread and passed
    // (aka file) thread.
    class FileThreadDeserializer
        : public base::RefCountedThreadSafe<FileThreadDeserializer>
    {
    public:
        FileThreadDeserializer(JsonPrefStore* delegate,
            base::MessageLoopProxy* file_loop_proxy)
            : no_dir_(false),
            error_(PersistentPrefStore::PREF_READ_ERROR_NONE),
            delegate_(delegate),
            file_loop_proxy_(file_loop_proxy),
            origin_loop_proxy_(base::MessageLoopProxy::current()) {}

        void Start(const FilePath& path)
        {
            DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
            file_loop_proxy_->PostTask(
                NewRunnableMethod(this,
                &FileThreadDeserializer::ReadFileAndReport,
                path));
        }

        // Deserializes JSON on the file thread.
        void ReadFileAndReport(const FilePath& path)
        {
            DCHECK(file_loop_proxy_->BelongsToCurrentThread());

            value_.reset(DoReading(path, &error_, &no_dir_));

            origin_loop_proxy_->PostTask(
                NewRunnableMethod(this, &FileThreadDeserializer::ReportOnOriginThread));
        }

        // Reports deserialization result on the origin thread.
        void ReportOnOriginThread()
        {
            DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
            delegate_->OnFileRead(value_.release(), error_, no_dir_);
        }

        static base::Value* DoReading(const FilePath& path,
            PersistentPrefStore::PrefReadError* error,
            bool* no_dir)
        {
            int error_code;
            std::string error_msg;
            JSONFileValueSerializer serializer(path);
            base::Value* value = serializer.Deserialize(&error_code, &error_msg);
            HandleErrors(value, path, error_code, error_msg, error);
            *no_dir = !base::PathExists(path.DirName());
            return value;
        }

        static void HandleErrors(const base::Value* value,
            const FilePath& path,
            int error_code,
            const std::string& error_msg,
            PersistentPrefStore::PrefReadError* error);

    private:
        friend class base::RefCountedThreadSafe<FileThreadDeserializer>;

        bool no_dir_;
        PersistentPrefStore::PrefReadError error_;
        scoped_ptr<base::Value> value_;
        scoped_refptr<JsonPrefStore> delegate_;
        scoped_refptr<base::MessageLoopProxy> file_loop_proxy_;
        scoped_refptr<base::MessageLoopProxy> origin_loop_proxy_;
    };

    // static
    void FileThreadDeserializer::HandleErrors(
        const base::Value* value,
        const FilePath& path,
        int error_code,
        const std::string& error_msg,
        PersistentPrefStore::PrefReadError* error)
    {
        *error = PersistentPrefStore::PREF_READ_ERROR_NONE;
        if(!value)
        {
            VLOG(1) << "Error while loading JSON file: " << error_msg;
            switch(error_code)
            {
            case JSONFileValueSerializer::JSON_ACCESS_DENIED:
                *error = PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
                break;
            case JSONFileValueSerializer::JSON_CANNOT_READ_FILE:
                *error = PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
                break;
            case JSONFileValueSerializer::JSON_FILE_LOCKED:
                *error = PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
                break;
            case JSONFileValueSerializer::JSON_NO_SUCH_FILE:
                *error = PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
                break;
            default:
                *error = PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
                // JSON errors indicate file corruption of some sort.
                // Since the file is corrupt, move it to the side and continue with
                // empty preferences.  This will result in them losing their settings.
                // We keep the old file for possible support and debugging assistance
                // as well as to detect if they're seeing these errors repeatedly.
                // TODO(erikkay) Instead, use the last known good file.
                FilePath bad = path.ReplaceExtension(kBadExtension);

                // If they've ever had a parse error before, put them in another bucket.
                // TODO(erikkay) if we keep this error checking for very long, we may
                // want to differentiate between recent and long ago errors.
                if(base::PathExists(bad))
                {
                    *error = PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT;
                }
                base::Move(path, bad);
                break;
            }
        }
        else if(!value->IsType(base::Value::TYPE_DICTIONARY))
        {
            *error = PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
        }
    }

}

JsonPrefStore::JsonPrefStore(const FilePath& filename,
                             base::MessageLoopProxy* file_message_loop_proxy)
                             : path_(filename),
                             file_message_loop_proxy_(file_message_loop_proxy),
                             prefs_(new base::DictionaryValue()),
                             read_only_(false),
                             writer_(filename, file_message_loop_proxy),
                             error_delegate_(NULL),
                             initialized_(false) {}

JsonPrefStore::~JsonPrefStore()
{
    CommitPendingWrite();
}

PrefStore::ReadResult JsonPrefStore::GetValue(const std::string& key,
                                              const base::Value** result) const
{
    base::Value* tmp = NULL;
    if(prefs_->Get(key, &tmp))
    {
        if(result)
        {
            *result = tmp;
        }
        return READ_OK;
    }
    return READ_NO_VALUE;
}

void JsonPrefStore::AddObserver(PrefStore::Observer* observer)
{
    observers_.AddObserver(observer);
}

void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer)
{
    observers_.RemoveObserver(observer);
}

bool JsonPrefStore::IsInitializationComplete() const
{
    return initialized_;
}

PrefStore::ReadResult JsonPrefStore::GetMutableValue(const std::string& key,
                                                     base::Value** result)
{
    return prefs_->Get(key, result) ? READ_OK : READ_NO_VALUE;
}

void JsonPrefStore::SetValue(const std::string& key, base::Value* value)
{
    DCHECK(value);
    scoped_ptr<base::Value> new_value(value);
    base::Value* old_value = NULL;
    prefs_->Get(key, &old_value);
    if(!old_value || !value->Equals(old_value))
    {
        prefs_->Set(key, new_value.release());
        FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
    }
}

void JsonPrefStore::SetValueSilently(const std::string& key, base::Value* value)
{
    DCHECK(value);
    scoped_ptr<base::Value> new_value(value);
    base::Value* old_value = NULL;
    prefs_->Get(key, &old_value);
    if(!old_value || !value->Equals(old_value))
    {
        prefs_->Set(key, new_value.release());
    }
}

void JsonPrefStore::RemoveValue(const std::string& key)
{
    if(prefs_->Remove(key, NULL))
    {
        FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
    }
}

bool JsonPrefStore::ReadOnly() const
{
    return read_only_;
}

void JsonPrefStore::OnFileRead(base::Value* value_owned,
                               PersistentPrefStore::PrefReadError error,
                               bool no_dir)
{
    scoped_ptr<base::Value> value(value_owned);
    initialized_ = true;

    if(no_dir)
    {
        FOR_EACH_OBSERVER(PrefStore::Observer,
            observers_,
            OnInitializationCompleted(false));
        return;
    }

    switch(error)
    {
    case PREF_READ_ERROR_ACCESS_DENIED:
    case PREF_READ_ERROR_FILE_OTHER:
    case PREF_READ_ERROR_FILE_LOCKED:
    case PREF_READ_ERROR_JSON_TYPE:
    case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
        read_only_ = true;
        break;
    case PREF_READ_ERROR_NONE:
        DCHECK(value.get());
        prefs_.reset(static_cast<base::DictionaryValue*>(value.release()));
        break;
    case PREF_READ_ERROR_NO_FILE:
        // If the file just doesn't exist, maybe this is first run.  In any case
        // there's no harm in writing out default prefs in this case.
        break;
    case PREF_READ_ERROR_JSON_PARSE:
    case PREF_READ_ERROR_JSON_REPEAT:
        break;
    default:
        NOTREACHED() << "Unknown error: " << error;
    }

    if(error_delegate_.get() && error != PREF_READ_ERROR_NONE)
    {
        error_delegate_->OnError(error);
    }

    FOR_EACH_OBSERVER(PrefStore::Observer,
        observers_,
        OnInitializationCompleted(true));
}

void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate *error_delegate)
{
    initialized_ = false;
    error_delegate_.reset(error_delegate);
    if(path_.empty())
    {
        OnFileRead(NULL, PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
        return;
    }

    // Start async reading of the preferences file. It will delete itself
    // in the end.
    scoped_refptr<FileThreadDeserializer> deserializer(
        new FileThreadDeserializer(this, file_message_loop_proxy_.get()));
    deserializer->Start(path_);
}

PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs()
{
    if(path_.empty())
    {
        OnFileRead(NULL, PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
        return PREF_READ_ERROR_FILE_NOT_SPECIFIED;
    }

    PrefReadError error;
    bool no_dir;
    base::Value* value = FileThreadDeserializer::DoReading(path_, &error, &no_dir);
    OnFileRead(value, error, no_dir);
    return error;
}

bool JsonPrefStore::WritePrefs()
{
    std::string data;
    if(!SerializeData(&data))
    {
        return false;
    }

    // Lie about our ability to save.
    if(read_only_)
    {
        return true;
    }

    writer_.WriteNow(data);
    return true;
}

void JsonPrefStore::ScheduleWritePrefs()
{
    if(read_only_)
    {
        return;
    }

    writer_.ScheduleWrite(this);
}

void JsonPrefStore::CommitPendingWrite()
{
    if(writer_.HasPendingWrite() && !read_only_)
    {
        writer_.DoScheduledWrite();
    }
}

void JsonPrefStore::ReportValueChanged(const std::string& key)
{
    FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
}

bool JsonPrefStore::SerializeData(std::string* output)
{
    // TODO(tc): Do we want to prune webkit preferences that match the default
    // value?
    JSONStringValueSerializer serializer(output);
    serializer.set_pretty_print(true);
    scoped_ptr<base::DictionaryValue> copy(prefs_->DeepCopyWithoutEmptyChildren());
    return serializer.Serialize(*(copy.get()));
}